Tilting type electric induction furnace



29, 1950 l. HARTER, JR ET AL 2,520,598

TILTING TYPE ELECTRIC INDUCTION FURNACE Filed May 8, 1947 4 Sheets-Sheet1 Sid/2g 015761225 VENTORS 5 7 ATTORNEY Filed May 8, 1947 A 9, 1950 I.HARTER, JR ETAL 2,520,598

TILTING TYPE ELECTRIC INDUCTION FURNACE 4 Sheets-Sheet 2 INVENTORS BY44L ATTORNEY 4 Sheets-Sheet 3 l. HARTER, JR EI'AL Q [Vans TILTING TYPEELECTRIC INDUCTION FURNACE Aug. 29, 1950 Filed May 8, 1947 INVENTORSATTORN EY 0 [same Harzfz; Jr &

Sid/e 1950 i. HARTER, JR ETAL 2,520,598

TILTING TYPE ELECTRIC INDUCTION FURNACE Filed May 8, 1947 4 Sheets-Sheet4 ooooc-Qoooooo [9000 Harzfezfi & Sid/e 0 [Vans INVENTORS BY W ATTORNEYPatented Aug. 29, 1950 UNITED STATES PATENT orries TILTING TYPE ELECTRICINDUCTION FURNACE lsaac Harrier, .lr., and Sidley 0. Evans, Beaver, Pa,assignorsto The Balacock & Wilcox Tube (Company, West Mayiield, Pa., acorporation of Pennsylvania Application May 8, 1947, Serial No. 746,810

the holding and heating of molten metal for lip pour metal delivery at acontrolled rate to a selected position and at a substantially uniformmetal delivery temperature.

In accordance with ourinvention we provide a lip pour tilting type ofmolten metal holding furnace which is arranged for an accurateregulation of metal delivery therefrom. The rate of metal flow from thefurnace is not only controllable by regulation of the furnace tiltingangle, but we further provide a horizontally adjustable axis of tiltingrotation for the furnace which can be regulated to control the deliverypoint of the metal poured. In additionwe provide electric inductionheating of the molten metal within the furnace so as to establish andmaintain the metal therein at an optimum pouring temperature. The moltenmetal temperature is maintained substantially uniform during thefurnacepouring period by a continuation of the induced heating effect. This-isaccomplished by providing flexible power leads and cooling waterconnections to the furnace and a proper regulation of electric powerinput to the furnace during its tilting motion. Advantageously, thefurnace -is ofan economical and lightweight construc- .tion wherein theselection of materials and the arrangement of parts provides afurnacethat is easy to handle during its tilting movement whilebeingsafe to operate and has an electricalefiiciencycomparable-with-much heavier and more elaborate.constructions.

Theprincipal object of-the present invention isto provide an electricinduction furnace of the tilting type for pouring. molten metalwhich iscapable of establishing andmaintaining an optimum temperature of moltenmetal therein during the pouring period. An. additional and morespecific object is to provide an electric induction furnaceof thetilting typev which is adapted for the delivery of molten metal at apredetermined substantially uniform temperature and controlled rate ofdelivery to a substantially uniformly positioned metal receiving.position' An additional object is.to provide a lightweight electricinduction furnace of the lip pouring type which is tiltable about ahorizontally adjustable transverse axis wherein the angle of tilt andthe position of .the axis are adjustable for a controlled delivery ofmolten metal to a predetermined fixed position.

The various .features of novelty which characterize our invention arepointed out with particularity'in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings anddescriptivermatter in which we have illustrated and described apreferred embodiment of our invention.

Of the drawings:

Fig.1 is a side elevation view of an electric induction furnaceconstructed in accordance with the present invention;

Fig. 2 is a front elevation view of the electric induction furnace shownin Fig. 1;

Fig. 3 is an elevation, partly in section, of a portion of the apparatusshown in Fig. 1; and

Fig.4 is a section taken on line ii of Fig. 3.

In general'the present invention includes an electric induction furnacell of the lip pour type which is securely mounted upon a tilting frameH. The frame and furnace are tiltable as a unit about a horizontal axiswhich intersects the lower surface of a V notch pouring lip l2positioned in the upper portion of the furnace wall, and 'is normal tothe direction of molten metal discharge. The axis of tilt is adjustablein a horizontal plane so that the molten metal stream discharged fromthe furnace may be d livered to a substantially fixed position duringthefurnace tilting movement. The furnace is of the induction electricheating type and is provided with flexible electric power and coolingfluid connections whereby metal heating by elec trical energy'may becontinued during the pouring period. Such a furnace is particularlyadvantageous in the continuous casting of high melting temperaturemetals, such as steel.

An arrangement of the apparatus for the continuous casting of steel,incorporating the electric induction furnace of thepresent invention isdisclosed in a co-pending application of I. Harter, I. Harter, Jr., andO. R. Carpenter, Serial No. 10,956, filed February 26, 1.948. Asdescribed in said application and shown in Figs. 1 and 2-, the inductionfurnace H3 is arranged to deliver molten metal to a tun dish l3 andthence continuously cast in a water cooled mold assembly Hi. With thefurnace l9 constructed and operated as hereinafter described, moltenmetal discharged from the furnace is maintained at'a substantiallyuniform temperature and at a controlled discharge rate for"delivery tothe tun dish I3. As shown particularly in Figs. 3 and l the furnace hasa central cylindrical molten steel holding space which has a capacity,below the level of the pouring lip l2, of approximately 6000 lbs. Thefurnace consists of the central cylindrical metal holding and heatingreceptacle which is supported in spaced relationship within an embracingstructure as hereinafter described.

The metal holding and heating receptacle includes a cylindrical wallmade up of radially positioned rows of preformed refractory blocks ortile l5, a monolithic ceramic layer it, and a hollow helical metalliccoil H. The successive turns of the coil ll are closely spaced topresent a substantially continuous metallic inner face in embracing andsupporting relationship to the monolithic layer I6. The bottom of thecylindrical receptacle is formed by a plurality of layers of preformedtile indicated at 25, which extends transversely between and ininterlocking relationship with the lower portion of the inner row oftile i5. A layer of heat insulating material 2'! is correspondinglyarranged below and in supporting relationship with the tile 25. Theinsulation 21, the lowermost tiles l5, and the lower portion of themonolithic layer l6 which extends outwardly in supporting relation tothe lowermost turns of coil are all supported by a transverselyextending plate member 28 which is a part of the supporting structure aswill be hereinafter described in detail.

The hollow helical coil H is of copper and of rectangular section,having a vertical outside dimension of 2% inches and a transversedimension of 1 inch, the metal wall thickness being of the order ofinch. The successive turns of the coil are spaced apart approximatelyinch by an asbestos tape l8 which is of sufilcient thickness to provideadequate electrical insulation between the successive turns. Theadjacent turns of the coil provide proper circumferential support forthe enclosed monolithic layer is and a cooling surface for theextraction of heat, thereby maintaining the molten metal holdingintegrity of the refractory lining of the cylindrical receptacle. Thelowermost turns of the coil extend below the level of the bottom tile 26so as to impose a corresponding cooling action upon the circumferentialportions thereof. A flow of cooling water through the hollow coil H ismaintained when the furnace or receptacle is in use, the water beingintroduced at the top and discharged from the bottom of the coil ashereinafter described.

The supporting structure for the metal receptacle is of box-likearrangement made up of a combination of non-metallic and metallic partsarranged to provide structural strength while avoiding a relation ofmetallic parts which will permit the generation of appreciable inducedelectrical currents by the magnetic field from the furnace heating coil.The bottom of the structure, which rests upon the tilting framecomprises marginal metallic members 3|] and the transverse I-sectionmembers 29 arranged to support the plate member 28.

The four sides of the structure comprise members 2| which are formed ofa single piece of non-metallic non-combustible temperature resistantmaterial extending from their respective bottom angles 38 to which theyare bolted to the top of the receptacle. Metallic corner angles 22 andthe embracing sectional metallic bands 32 bind the four sides 2| into arigid box-like structure. The outer circular wall of the receptacleincluding the pouring lip I2 is positioned against the inside of amember 2 I, as at 39, while the opiii posite side of the cylindricalcontainer, as well as the transverse sides, are positioned away from themembers 2| by non-metallic space blocks 24. The blocks 24 bear on theoutside of the coil turns and extend throughout the full height of themembers 2|. At intermediate circumferential positions, additional radialsupporting and restraining space members 23 extend between the outersurfaces of the coil turns and the inner corner of angles 22, themembers 23 being coextensive with the height of the members 2| formingthe embracing box.

The non-metallic material used for the members 2|, 23, 24 and 28 is ofcemented asbestos, the ingredients being so proportioned that thestructural units have qualities of high density, electrical insulation,heat insulation, good strength, and heat resistance. The metallic angles30 which are bolted to the bottom of members 2| and member 28 are oflimited length and spaced apart so as to avoid a closed metallic loopfor induced currents. The plurality of bands 32, of which the lowermostembraces the lower edges of members 2|, are vertically spaced, eachbeing bolted at spaced position to the members 2| and the corner angles22. Each band 32 is made in a plurality of segments which are boltedtogether and electrically insulated from one another by the use of aninsulating gasket as indicated at 33.

The furnace H3 is securely affixed to the tilting frame I so as toremain in a fixed position relative to the frame during the tiltingmotion of the assembly. The frame is formed with a structural steelplatform 34 from one end of which a spaced pair of arm members 35 areperpendicularly extended. The arms are connected by a ribbed plate 36intermediate their height. The furnace is held in position on the frameH by a pair of anchor rods 31, each of which extends along one side ofthe furnace and is attached at opposite ends to the plate 36 and atransverse member 31'. A channel member 38 forms the end of the platform34 and extends above the upper surface of the platform to provide a footbrace for the front wall of the furnace. The shifting weight of moltenmetal within the furnace I0 resulting from its tilting motion is thustransmitted to the tilting frame.

The upstanding arm members 35 of the frame are each provided with atrunnion 40 extending outwardly on either side of the furnace andengaging a corresponding trunnion bearing 4| mounted on a pedestal 42.The trunnions 40 provide an axis of rotation X-X about which theassembly of the frame and furnace is tilted to pour metal through thelip I2. The lower edge of the lip lies on the axis X-X of tiltingrotation. The trunnion bearings 4| are arranged to be slidable in ahorizontal direction on guides 43 which are affixed to the upper ends ofthe pedestals. The horizontal position of both of the bearings issimultaneously regulated by individual adjusting screws 44 operated by apair of interlocked reversing type motors (not shown). The tiltingmovement of the furnace about its axis X--X is obtained through movementof a cable 45 which is attached to a cable yoke 46 affixed to one end ofthe frame remote from the axis of tilting rotation. The cable 45 ispassed through a differential chain block 41 and is wrapped about agrooved hoisting drum 48 rotated by a reversible motor-driven geardrive. The block 4! is supported from the underside of a supportingframework 50 for the drum 48 and it is driven and so spaced above thefurnace that the furnace may be tilted at an angle of the use of aplurality of flexible electric cables 5! which are attached alternatelyto water cooled bus bars 52 and 53 secured to the frame II and connectedwith the coil H as hereinafter described. From the water cooled bus bars'52 and 53 the cables 5-! are passed. over a :grooved d-rum 54, which ismounted in the platform 34, and over a grooved drum 55 which isrotatably mounted upon the supporting framework 56 for the pedestals 42.The cables 5| are looped downwardly below the level of the framework 56and at the bottom of the loop are provided with a grooved drum 5'! whichacts as a counterweight to maintain proper alignment and to preventkinking of the cables during the tilting movement of the furnace. Thecables are separately attached to a pair of bus bars t8 which areaffixed to the framework 55 in opposite relationship to bars '52 and 53and are connected to a conventional control and frequency generatingpower source located at :a conveniently lower level (not shown). Thusthe cables are of equal length and their alternate arrangement minimizesreactance losses. The cooling water connections to the bus bars 52 and53 on the furnace frame H' are connected by means of rubber hoses tiland 6] to a source of water supply and a water discharge connection (notshown) outwardly adjacent a trunnion ll].

The bus bars 52 and 53 mounted on the furnace frame are supported byelectrical insulators 62 mounted upon wooden beams 63 extendingtransversely across the frame H. One end of each bus bar is connected toa corresponding fitting for the rubber hoses 6B and 6| while theopposite end of each bus bar is provided with a copper pipe 6d and 65leading to the coil ll. As shown particularly in Fig. 4, one of thepipes it is connected to the upper end of the coil ['7 while the otherpipe 65 is connected at two vertically spaced positions in the lowerportion of the coil. It will be noted that the coil is provided withseveral turns in its lower portion which extend below the level of theupper surface of the refractory furnace bottom 25. One of theconnections 56 from the copper pipe 65 is secured to a coil turn atapproximately the level of the furnace bottom while the otherconnectioniil from the pipe 65 extends to the lowermost turn of the coil51. The connection so is through a solid copper stud to prevent a now ofWater therethrough and to provide sufficient cross-sectional area tocarry current without over heating. Between the levels of the two coilconnections the pipe 65 is provided with a short section of rubber hose68 which is clamped at opposite ends to spaced sections of the pipe 65.In this manner the pipe provides an electrical connection 66 to one-coilturnand provides a water connection 6! to the lowest coil turn in thelower portion of the furnace. The electrical connection to the lowestcoil turn is broken by the insertion of the rubber hose section 68. Thuscooling water is circulated through the full length of the coil whilethe electric circuit extends from approximately the level of the bottom2510f the furnace to the upper end of the coil [1. This arrangementprovides a cooling effect to-the furnace refractory bot-tom aspreviously described.

In operation, the furnace it is preheated by the use of a separateheating source, such as by burning gas, and then charged with moltenmetal. Electric power, at for example 400 to .800 volts and 750 to 1000cycles, and cooling water are supplied to the coil. The cooling waterflow is adjusted to maintain the coil temperature .at

an operating level at maximum power input conditions and once thedesired flow rate is established it is maintained at the same value:regardless of any reduction in the electric energy input.

After the metal has been brought to the desired pouring temperature andhas been deoxidized, the furnace is tilted by operating the hoist drum48. The stream of metal poured from the furnace lip "l2 enters andpasses through the tun dish :3, wherein a slag dam traps the slag andthe molten metal is poured into the mold i l. The point of steeldelivery into the'tun dish i3 is advantageously regulated by adjustingthe position of the trunnions '48 on the pedestals :22, thus changingthe position of the axis 'X-X relative to the tun dish. The regulationof the position of the axis X-X and the angle of tilt may beaccomplished simultaneously or separately, as desired, to obtain aproper delivery of molten steel, both as to the rate of new and theposition of delivery.

As the furnace is tilted, the position of the molten steel within thefurnace shifts and the volume of steel is progressively reduced. Sincethe steel serves as a secondary circuit for the induction heating, theheating effect is diminished with the reduction and shifting of themolten steel charge. This will result in an increase in the voltage ofthe electric power supplied to the coil H. We have found that-rnanuallyor automatically regulating the impressed voltage on the coil tomaintain a substantially uniform voltage during the tilting motion. ofthe furnace will proportionately reduce the induced heating eifect tomaintain the temperature of the steel within close limits through amajor portion of the pouring period.

In the furnace shown, the pouring temperature of the steel has beenrepeatedly maintained within a temperature range of 20 F. from the startof the pouring period to the last few minutes of pouring. During a shortperiod at the very end of the pouring period the charge of molten steelwithin the furnace is so reduced as to effectively eliminate anyelectric induction heating thereof so that the power is cut It will benoted that we provide an electric induction furnace of the coreless typewhich is characterized by its lightweight and economical construction. Ahollow copper conductor of rectangular cross-section is wound in ahelical coil with its closely spaced turns separated. by a strip ofinsulating material. The coil embraces an internal lining of refractorymaterial forming a cylindrical furnace wall to hold a molten metalcharge therein. The electrical and water connections to the coil arearranged to heat the molten metal within the furnace and to providecooling for the refractory materials forming the furnace. The lowerturns of the coil between the connections 66 and 6'! particularlyprovide an eifective means for cooling the lower portion of the members2!. A lightweight box-like supporting structure of square horizontalcross-section encloses and positions the cylindrical coil with the lippouring side of the furnace coil abutting one side of the box. The coilis spaced from the other sides of the box and maintained in position bya series of circumferentially spaced blocks.

The furnace is mounted upon a tilting frame which is arranged forrotational movement about a horizontal axis passing through trunnionsprojecting outwardly of the frame. The axis is adjustable in ahorizontal plane and intersects the lower surface of the furnace pouringlip. The weight of molten steel within the furnace is transmittedthrough the furnace wall and the exterior supporting structure to theupstanding arms of the tilting frame. The electric and cooling Waterconnections to the furnace coil are flexible for a continuation of theelectric induction heating of the molten metal during the pouringperiod. As a result the molten steel is maintained at a substantiallyuniform optimum pouring temperature during the tilting motion of thefurnace.

While in accordance with the provisions of the statutes We haveillustrated and described herein the best form of the invention nowknown to us, those skilled in the art will understand that changes maybe made in the form of the apparatus disclosed without departing fromthe spirit of the invention covered by our claims, and that certainfeatures of our invention may sometimes be used to advantage without acorresponding use of other features.

We claim:

1. An electric induction furnace of the lip pour tilting type comprisingrefractory material defining the wall of said furnace, a hollow electricconductor coil embracing said walls, means for circulating cooling fluidthrough said hollow electric conductor, means for tilting said furnaceabout a horizontal axis, and means for maintaining the temperature ofmetal within said furnace substantially uniform during the tiltingmotion thereof including a pair of spaced bus bars each rigidlyconnected with one end of said coil, a plurality of flexible cableselectrically connecting a fixed position source of power supply withsaid bus bars, with alternate cables con nected to each of said bus barsfor flow of electric power to said coil, and a counterweighted grooveddrum suspended by and within a loop of each of said cables to maintainthe alignment and relative spacing of said cables during the tiltingmotion of said furnace.

2. An electric induction furnace of the lip pour tilting type comprisingrefractory walls defining the sides of said furnace, a refractory bottomand a removable refractory top for said furnace, a hollow electricconductor coil embracing said walls and extending from a spaced positionbelow the pouring lip to a spaced position below the bottom of saidfurnace, a cooling fluid connection to each end of said coil arranged tocause flow of said fluid through the full length of the coil, anelectrical connection to the upper end of said coil, a second electricalconnection to said coil at a position spaced above the lowermost turnsof said coil and substantially at the level of said furnace bottom,means for electrically insulating the coil portion below said secondelectrical connection from the portion of the coil above said secondelectrical connection, means for tilting said furnace, and means formaintaining the electrical and cooling fluid connections to said coilduring the tilting of said furnace.

3. An electric induction furnace of the lip pour tilting type comprisingrefractory walls defining the sides of said furnace, a refractory bottomand a removable refractory top for said furnace, a helical hollowelectric conductor coil embracing said walls and extending from a spacedposition below the pouring lip to the bottom of said furnace walls belowthe inner surface of said refractory furnace bottom, the adjacent turnsof said coil spaced apart by a strip of dielectric material, a casing ofcemented asbestos material enclosing said coil, a copper pipe connectedto the upper end of said coil arranged to provide a flow path forelectricity and cooling fluid, a second copper pipe connected with thelowermost turn of said coil to provide a flow path for cooling fluid, asolid copper stud connecting said second pipe with a coil turn upwardlyspaced from said lowermost turn of said coil to provide a flow path forelectricity, an electrically insulating section in said second pipebetween its fluid flow connection with said lowermost coil turn and saidsolid copper stud, means for tilting said furnace, and means formaintaining electrical and cooling fluid connections to said copperpipes during the tilting of said furnace.

ISAAC HARTER, JR, SIDLEY O. EVANS.

REFERENCES CITED The following references are of record in th file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 16,054 Moore Apr. 28, 1925876,946 Custer Jan. 21, 1908 1,008,406 Davis NOV. 14, 1911 1,068,643Franklin July 29, 1913 1,113,134 Moody Oct. 6, 1914 1,126,079 QueneauJan. 26, 1915 1,456,851 Kettering May 29, 1923 1,681,950 Northrup Aug.28, 1928 1,682,388 Lincoln Aug. 28, 1928 1,783,128 Morgan Nov. 25, 19301,849,476 Brace Mar. 15, 1932 1,884,637 Feehan Oct. 25, 1932 1,395,421Northrup Jan. 24, 1933 1,905,204 Zinno Apr. 25, 1933 1,926,573 WillcoxSept. 12, 1933 1,942,550 Helgeby Jan. 9, 1934 1,996,623 Lindner Apr. 2,1935 2,014,349 Wyatt Sept. 10, 1935 2,073,597 Northrup Mar. 9, 19372,433,495 Vogel Dec. 30, 1947 FOREIGN PATENTS Number Country Date297,311 Great Britain Apr. 4, 1929 392,764 Great Britain May 25, 1933615,418 Germany July 4, 1935

